In mammalian animals, the heart is a hollow muscular organ having four pumping chambers: the left and right atria and the left and right ventricles, each provided with its own one-way valve. The natural heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary valves, and each has leaflets to control the directional flow of blood through the heart. The valves are each supported by an annulus that comprises a dense fibrous ring attached either directly or indirectly to the atrial or ventricular muscle fibers. Various surgical techniques may be used to repair a diseased or damaged valve. In a valve replacement operation, the damaged leaflets are often excised and the annulus sculpted to receive a replacement valve. Sometimes the leaflets are heavily calcified and are left in place. Various types and configurations of prosthetic heart valves for replacing diseased natural human heart valves are known.
Two primary types of heart valve replacements or prostheses which include valve leaflets are those which have one or more relatively rigid leaflets formed of a stiff biocompatible material, and those which have flexible leaflets, typically made of a biological material. In the latter bioprosthetic or tissue valves, a whole xenograft valve (e.g., porcine) or a plurality of xenograft leaflets (e.g., bovine pericardium) provide occluding surfaces. Research is ongoing on synthesizing the tissue leaflets, and therefore the term “flexible leaflet valve” refers to both natural and artificial valves. Flexible leaflet valves may have a semi-rigid or relatively flexible frame or stent with (typically) three leaflets attached thereto, while some have no stent (stentless). In the former, the stent typically defines commissure posts projecting in an outflow direction that provide support between adjacent leaflets, and a substantially circular base surrounded by an annular or scalloped sewing ring for suturing the valve to surrounding tissue.
Examples of bioprosthetic valves are described in U.S. Pat. No. 4,106,129 to Carpentier et al., entitled “Supported Bioprosthetic Heart Valve with Compliant Orifice Ring,” and in U.S. Pat. No. 5,037,434 to Lane, entitled “Bioprosthetic Heart Valve with Elastic Commissures.” The Carpentier et al. '129 patent describes a stent comprising a single flexible wire preformed to define a generally circular base that is interrupted at circumferentially-spaced points by three inverted U-shaped commissure posts that project generally normally in the outflow direction with respect to the circular base. The Lane '434 patent describes a stent composed of a flexible metal ribbon similarly preformed to define three commissure posts that project generally normally with respect to a generally circular base. Both the Lane '434 and Carpentier et al. '129 patents describe a conventional configuration of three leaflets, wherein one leaflet is disposed between each pair of commissure posts.
To facilitate the implantation of heart valve prostheses, various types of specialized holders have been developed. Aortic valve holders are designed to enable the implanting surgeon to precisely position the heart valve and sewing ring either within the heart passageway or adjacent/above the aortic root of the patient and to securely hold the valve assembly in place until suturing is complete and the sutures are tied off.
Due to the usual approach through the aortic arch to the aortic annulus, holders for aortic valves are attached to the outflow end of the valve; i.e., the end having the commissure tips, and the valve advances with its inflow end leading. An elongate handle connects to the holder and is grasped and manipulated by the surgeon to maneuver the valve to its desired implantation position. The handle is then removed and the sewing ring sutured to the native valve annulus with the holder remaining attached to protect the valve. Certain shortcomings are associated with conventional aortic valve holders, including the presence of the holder that sometimes gets in the way out of the suturing operation. The holder as well as the upwardly projecting commissure posts can obstruct the surgeon's access to the valve base, making suturing of the sewing ring to surrounding tissue and tying-off of the implanting sutures difficult. Bulky holders may actually increase the potential for puncture of one of the leaflets or improper suturing.
Often, a so-called “parachute” method is employed wherein a circular array of sutures is first secured to the annulus and then passed in the same distribution through the sewing ring while it is still outside the body. The valve is then lowered into place along the circular array of sutures. Once the sewing ring is properly positioned against the annulus, the handle is removed so that the surgeon can more easily tie off the sutures on the visible (outflow) side of the sewing ring. As mentioned, the holder remains to protect the valve during suture tie-down and to ensure valve shape. Even with such an elaborate procedure, there is precious little space between the upstanding commissures and leaflets of the valve and the surrounding aortic wall for the surgeon to manipulate forceps to tie off the sutures. This is particularly evident in patients having a relatively small aortic root, and is exacerbated by bulky holders.
Some attempts at mitigating the sometimes obtrusive nature of aortic valve holders have been made. For example, U.S. Pat. No. 5,716,401 to Eberhardt, et al. discloses a holder for an aortic valve having a plurality of distally-projecting fingers adapted to engage the commissure posts of the valve. The fingers displace the commissure posts radially inward, and a mechanism is provided for retaining the fingers in that inward position, thus reducing obstacles to the surgeon's suturing operation. The Eberhardt holder is relatively complicated, however, and adds cost to the valve.
What is needed then is an elegant prosthetic aortic valve holder attachable to the outflow end of the valve that enhances visibility and facilitates implantation without the need for moving parts and the like.